Determine whether the rational root theorem provides a complete list of all roots for the following polynomial functions. f(x) = 4x2 − 25 g(x) = 4x2 + 25 h(x) = 3x2 − 25

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Answer:

on Quizlet:  1) yes   2) no, complex roots  3) no, irrational roots

Step-by-step explanation:


Rational root theorem is used to determine the possible root of a function.

  • Rational root theorem provides a complete list of all roots of [tex]\mathbf{(a)\ f(x)= 4x^2 - 25}[/tex]
  • Rational root theorem does not provide a complete list of all roots of [tex]\mathbf{(b)\ g(x)= 4x^2 + 25}[/tex]
  • Rational root theorem does not provide a complete list of all roots of [tex]\mathbf{(c)\ h(x)= 3x^2 - 25}[/tex]

[tex]\mathbf{(a)\ f(x)= 4x^2 - 25}[/tex]

Set to 0

[tex]\mathbf{4x^2 - 25 = 0}[/tex]

Add 25 to both sides

[tex]\mathbf{4x^2 = 25}[/tex]

Divide both sides by 4

[tex]\mathbf{x^2 = \frac{25}{4}}[/tex]

Take square roots

[tex]\mathbf{x = \pm\frac{5}{2}}[/tex]

The function has rational roots.

This means that: rational root theorem provides a complete list of all roots

[tex]\mathbf{(b)\ g(x)= 4x^2 + 25}[/tex]

Set to 0

[tex]\mathbf{4x^2 + 25 = 0}[/tex]

Add -25 to both sides

[tex]\mathbf{4x^2 = -25}[/tex]

Divide both sides by 4

[tex]\mathbf{x^2 = -\frac{25}{4}}[/tex]

Take square roots

[tex]\mathbf{x = \pm \sqrt{-\frac{25}{4}}}[/tex]

The function has complex roots.

This means that: rational root theorem does not provide a complete list of all roots

[tex]\mathbf{(c)\ h(x)= 3x^2 - 25}[/tex]

Set to 0

[tex]\mathbf{3x^2 - 25 = 0}[/tex]

Add -25 to both sides

[tex]\mathbf{3x^2 = 25}[/tex]

Divide both sides by 4

[tex]\mathbf{x^2 = 8.333}[/tex]

Take square roots

[tex]\mathbf{x = \pm 2.89}[/tex]

The function has irrational roots.

This means that: rational root theorem does not provide a complete list of all roots

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